Shoot manipulations improve flushing and flowering of mandarin citrus in Indonesia

Mechanical shoot manipulations through bending and defoliation were applied on mandarin citrus cv. Borneo Prima in order to stimulate flushing and flowering during the rainy season, Oct. 2016-July 2017 in the tropical lowland of Indonesia. Four-year-old citrus trees were treated with bending, defoliation and its combination; and were replicated ten times with single tree as an experimental unit. All manipulated shoots exhibited rapid flushing, particularly of those with defoliation. Unfortunately, no flower was produced on trees treated with defoliation or its combination. Bending stimulated a larger number of flowering and fruiting trees than control. Flower drop was lower in bending, resulted in higher number of fruitset and fruitlets than control. At the generative stage, mandarin showed high C/N ratio due to low nitrogen content, irrespective of treatment. The failure to produce flower on defoliation and its combination could be ascertained by steady C/N ratio. Overall, bending could be applied to improve flowering and support sustainable mandarin production in tropical condition, especially at lowland production fields in Indonesia.